Customers have
commonly removed sags that were 3 and 4 inches deep. Most
customers say the majority of sags they encounter are less than 2
inches deep.The maximum amount of sag that can be removed may
vary with the job conditions. In some instances the pipe raises
relatively easy all of the way and other times the pipe may get
progressively more difficult to raise as it is lifted up.

At what
depths of bury will will the sag machine still work?

The depth of the pipe
does not appear to be a big issue. It has been used successfully
at depths exceeding 30 feet deep. One customer reported removing
a sag in an 8 inch line that was 45 feet deep.

How large of
diameter pipe can the machine be used on?

The sag machine comes
equiped for 8 inch pipe. We build adapters for 10 and 12 inch
pipe. Sags in 12 inch pipe can be slow and difficult to remove.

Sags on larger
diameter pipe are harder to remove. In order to remove a sag, the
machine has to bend the pipe. Larger pipes have more strength and
are more difficult to bend within the span of the sag machine. In
addition, larger diameter pipe bends in a longer radius, so more
length has to be lifted at the same time and as this length
increases, it gets farther from the vibrator.

What is the
success rate of the sag correction system?

The success rates
vary with the customer and their job conditions. It is important
that the pipe is surrounded with a granular material (crushed
rock or sand) and the material is saturated with water or water
is added as shown in the detail on the web site.

The sag machine
usually works very well where the pipe is deep and the water
table is above the top of the pipe. Most customers report success
rates of 90 to 100 percent in these conditions with 8 inch and 10
inch diameter pipe.

The machine also has
a high success rate in dry conditions where water is injected and
the granular pipe zone material contains fines.

Where water is
injected in dry conditions and the pipe zone material is coarse
or the fines are screened out, the success results are more
mixed. We think this could be from the material being too free
draining in proportion to the amount of water that was applied
and that not enough water was retained.

Where the machine has
been used in dry conditions without adding water, the results
have usually been poor. In most cases the machine will not work
dry, although some customers have reported examples where they
had success in dry conditions. Most experienced users tell us
that if they do not see results immediately, they start injecting
water.

Water helps lubricate
the pipe zone material to flow underneath the pipe. Also, water
helps transfer the vibration out into the surrounding material.
In dry conditions we have seen the pipe lift, but go back down
when the lift pressure was released.

There may be
conditions specific to certain sites that affect the results.
Feel free to call us to discuss your site conditions.

How long does
it take to remove a sag?

This will vary with
different conditions. Most experienced users tell us that it
takes them about a half of a day to set up and remove a typical
minor sag.

When assembling the
machine sections inside a manhole it may be necessary to chip out
part of the channel, to allow the sections to align and bolt
together. This may take more time if it is not done in advance.

Can I turn
the machine upside down and push down humps in the pipe?

No. The machine does
not work upside down. It would be necessary to feather out the
belly on the upstream side of the hump.

What types of
pipe will the machine work on?

The pipe must be
flexible so the machine can arch it up at the sag. Most of the
feedback we have received was on 3034 PVC. One customer
successfully removed a sag in a 10 inch C-900 PVC pipe. The
machine will not work on ductile iron or rigid pipe.

What else
will I need besides the sag correction system to remove a sag?

You will need a 75
CFM or larger air compressor, a 3/4 inch minimum diameter air
hose, and our air swivel, oiler & filter assembly. You will
also need a separate 3/8 inch air hose to activate the lift
mechanism. It is possible to pull the machine and hoses by hand,
but it is too much work for most people unless the sag is close
to the manhole. We recommend using a light duty winch or pulling
device to move the machine with rollers or pulleys at each end of
the pipe. A pull back line should be attached in case the machine
gets stuck. A TV camera will be necessary unless the sag is near
a manhole.

Do you offer
any on-site training?

We don't think any
special training is necessary. Most customers have been doing
fine by following the instructions. We can answer any questions
by phone if they arise. Like learning to operate any other
equipment, one should go slow and careful until they have some
experience.